When I discovered solution for hiss sound, I thought that is going to happen in loud environment as concerts. During the concert I tried to tweak snd_soc_msm_2x and found that deleting 'DEC3 Volume':1:85 and 'DEC4 Volume':1:85 gave me acceptable sound quality. But without deleting 'ADC3 Volume':1:0 and 'ADC4 Volume':1:0, every next records was without sound at all. Of course that make sense.
Today, I continued my investigation and figured out that with deleted four lines mentioned above camcorder will not record sound after phone call. Reboot was only solution. Further investigation showed me that 'DEC3 Volume' or 'DEC4 Volume' doesn't exist in JB snd_soc_msm_2x at all. So I tried to delete those lines completely from snd_soc_msm_2x in CM11. Tested video recording, phone call (even I'm in roaming) and looks like that everything works. Not sure, but even hiss sound during call is gone. Obviously xt92x handles sound differently than other moto_msm8960 devices and we cannot use the same settings.
Looking forward for concert next week with several snd_soc_msm_2x prepared.
Video recorded with 'DEC3 Volume':1:85 and 'DEC4 Volume':1:85
Video recorded without 'DEC3 Volume':1:85 and 'DEC4 Volume':1:85
snd_soc_msm_2x without 'DEC3 Volume'and 'DEC4 Volume'
Disadvantage is that recorded sound is not that loud as with deleted lines. Original snd_soc_msm_2x has several setting for different environment. Maybe devs can add ability to change that in settings.
Please test it. Just replace snd_soc_msm_2x in /system/etc/snd_soc_msm/. Any suggestions or better solutions are welcome